On the LG smartphone, we have the option of using the messages app in dark mode, where the whole design is mainly kept in dark colours.

Android 9 | LG UX 9.0
Dark Mode -  Open the  Messages -App
Dark Mode -  Open the  Menu
Dark Mode -  Tap on  Enable dark mode  /  Disable dark mode
  1. Open the Messages-App
  2. Open the Menu
  3. Tap on Enable dark modeDisable dark mode

LG Instructions